The SMR assault rifle is the hardest weapon to use in Call of Duty Black Ops 2 I have found so far. It is basically an inferior version of the FAL DSW (click for a guide for that weapon) as the SMR is semi automatic with a slower fire rate, more recoil but higher damage than the FAL DSW. It is a very passive rifle to say the least. This guide explains how to use the SMR well and what the best class setup is.